1. Field of the Invention
The present invention relates to identification and information storage systems, and more particularly to bar code systems utilising a combination of optical, magnetic and magneto-optical methods of information storage.
2. Description of Prior Art and/or Background Information
It is now commonplace to use optically scanned bar codes to identify, articles upon which the bar code is printed, embossed, engraved or otherwise applied. In a typical application, such as the identification of products being sold in a supermarket, a plurality of bars having one of two possible widths are printed onto the merchandise according to a predetermined code in order to represent a combination of alphanumeric characters. An example of such a code is the USS Code 39 shown in FIG 1, where two alphanumeric characters are encoded using combinations of bars having one of two possible widths according to the binary representations indicated in the figure.
These bar codes are typically read by a laser scanning device, or light pen which passes over the bar code, the light reflected therefrom being detected by a sensor which converts the reflected light intensity pattern generated into a binary code.
It will be appreciated from the foregoing that in order to provide unique identification to more than several thousand articles, the number of bars, and the length of the bar code will have to increase. Thus, a fundamental problem with these bar codes is the limited quantity of information which may be stored in a given area. A further limitation is that they are generally printed permanently on the article and there is no possibility of conveniently updating the information carried thereon.
It is known in the field of disk drives and other magnetic recording media to use a magnetic layer on a substrate to record binary data patterns into the magnetic layer which may be read by a suitable means, and also, commonly may be written to to erase and/or update the information stored therein.